1. Field of the Invention
The present invention relates to a dielectric filter, a composite dielectric filter and a duplexer used in high-frequency bands, and a communication apparatus including the same.
2. Related Art
FIGS. 14A, 14B, 14C, 14D, 14E show a structure of a prior art dielectric filter comprising a dielectric block, which is mainly used in the micro-wave band. In this figures, FIG. 14B is a front view in which the dielectric filter is vertically stood, FIG. 14A is an upper-surface view, FIG. 14C is a bottom view, FIG. 14D is a left-side view, and FIG. 14E is a right-side view. In these figures, a reference numeral 1 indicates a dielectric block. Resonance-line holes indicated by numerals 2a, 2b, and 2c are disposed in the dielectric block 1. And, resonance lines 5a, 5b, and 5c are disposed on the inner surfaces of the resonance-line holes 2a, 2b, and 2c. A ground electrode 3 is disposed on an outer surface of the dielectric block 1. External terminals 6 and 7 are also disposed on the outer surface of the dielectric block 1 at predetermined portion so as to be insulated from the ground electric 3. The external terminal 6 and the resonance line 5a make capacitive coupling, whereas the external terminal 7 and the resonance line 5c make capacitive coupling. This arrangement permits the dielectric filter having band-pass characteristics of three stage resonators.
In the prior art dielectric filter using such a dielectric block, when another circuit device is added to a dielectric filter having a basic structure shown in FIGS. 14A to 14E, for example, when an inductance device is disposed, the inductance device is provided by soldering a coil as an individual component to an electrode on a surface of the dielectric block, or by using an electrode pattern disposed on the surface of the dielectric block.
However, in the former structure, not only is an additional component necessary besides the dielectric block, but the higher the frequency band used, the extremely smaller the dielectric block. Thus, installation of the additional component is difficult from a viewpoint of production. In the latter structure, as the dielectric block is miniaturized, it become difficult to dispose a large inductance. Thus, when the dielectric block is further miniaturized, the formation of a conductor pattern on the surface thereof is difficult.
To overcome the above described problems, preferred embodiments of the present invention provide a dielectric filter, a composite dielectric filter, duplexer and a communication apparatus including the same, in which a desired characteristic can be easily obtained by providing a device with an inductance component in a dielectric block constituting a dielectric filter.
One preferred embodiment of the present invention provides a dielectric filter comprising: a dielectric block; a plurality of resonance lines aligned substantially in parallel in the dielectric block; and a conductor line disposed in the dielectric block so as not to be parallel to the longitudinal direction of the resonance lines, the conductor line being served as a device having an inductance component which is connected to a circuit comprising the resonance lines.
According to the above described structure and arrangement, although the conductor line disposed in non-parallel to the direction in which the resonance lines are aligned is disposed inside the dielectric block, it does not operate as a resonance line coupled to the resonance lines. On the other hand, the inductance component thereof is utilized. Since the conductor line is provided inside the dielectric block, as in the case of formation of the resonance lines, for example, a hole is formed in the dielectric block so as to easily make a minute line by electroless plating. Moreover, the conductor-line length can be set to be longer than that in the case of formation of an inductance component on a surface of the dielectric block by providing an electrode pattern and a large inductance can thereby be obtained, although the dielectric block is compact.
The above described dielectric filter may further comprise: a ground electrode disposed on a surface of the dielectric block; and an electrode disposed at an end of the conductor line and generating a capacitance component between the ground electrode and the electrode.
According to the above structure and arrangement, an LC circuit is formed of the inductance component of the conductor line and the capacitance component between the electrode provided at the conductor-line end and the ground electrode. For example, this structure permits a low pass filter, a high pass filter, or a band block filter (a trap) to be formed.
Another preferred embodiment of the present invention provides a composite dielectric filter comprising: a dielectric block; a first filter section comprising a plurality of resonance lines aligned substantially in parallel in the dielectric block; a conductor line disposed in the dielectric block so as not to be parallel to a direction in which the resonance lines are aligned in the dielectric block; a ground electrode disposed on a surface of the dielectric block; an electrode disposed at an end of the conductor line and generating a capacitance component between the ground electrode and the electrode; and a second filter section comprising an inductance component of the conductor line and the capacitance component.
According to the above structure and arrangement, for example, when the first filter section comprising the plurality of resonance lines aligned substantially in parallel is used as a band pass filter and the second filter section comprising the inductance component of the conductor line in the dielectric block and the capacitance component between the electrode at the conductor-line end and the ground electrode is used as a low pass filter, a composite dielectric filter in which the band pass filter and the low pass filter are combined can be obtained easily.
Yet another preferred embodiment of the present invention provides a composite dielectric filter comprising: a plurality of dielectric filters including the above described dielectric filter, or the above described composite dielectric filter, which are provided in a common dielectric block.
The above structure and arrangement, for example, permits a further miniaturized composite dielectric filter overall such as a diplexer, a duplexer, a multiplexer, or the like, to be obtained.
Yet another preferred embodiment of the present invention provides a duplexer having a transmission-signal input unit, a reception-signal output unit, and an antenna connection unit, in which the dielectric filter or the composite dielectric filter described above is used as a transmission filter and a reception filter.
Yet another preferred embodiment of the present invention provides a communication apparatus comprising the above described dielectric filter, the above described composite dielectric filter, or the above described duplexer disposed in a high-frequency circuit section.
The above structure and arrangement permit a compact and lightweight communication apparatus to be obtained.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.